Induction furnace monolithic refractory lining for copper and copper base alloy

Abstract

The present invention relates to a monolithic refractory lining for induction furnaces used in melting copper and copper-based alloys. It addresses challenges such as wear, corrosion, and thermal inefficiency in conventional refractory linings. The invention introduces a high-strength, durable refractory lining that eliminates the need for lengthy sintering cycles, reduces metal loss, and enhances thermal efficiency. It is compatible with various metals and alloys, promotes reusability of MS formers, and allows for faster installation and repair.

Description

"INDUCTION FURNACE MONOLITHIC REFRACTORY LINING FOR COPPER AND COPPER BASE ALLOY"TECHNICAL FIELD

[0001] The present disclosure relates to refractory materials. Specifically, it relates to a monolithic refractory lining optimized for copper and copper-based alloy furnaces to enhance durability, thermal efficiency, and erosion resistance.BACKGROUND

[0002] Refractory Linings for furnaces are used in copper industries / brass industries employing charge material of copper, brass, bronzes, zinc, lead, tin, nickel, aluminium, Iron, different ferro alloys, pure metal, degasser, N2, Argon gases as initial / late addition to produce copper and Copper base alloy, brass, bronzes etc.

[0003] Induction furnaces typically have refractory linings which protects their current carrying copper coils and cradle assembly from damage, erosion, chemical reactivity with the molten metal, mechanical forces of charge, electrical forces of induced eddy current, melting operations, holding of liquid metal, alloying, degassing, tilting for tapping, and reaction with slag.

[0004] Further, the refractory linings experience wear, tear and localised damage from melting process / exposure to molten metal, which periodically requires to be repaired or replaced.

[0005] A conventional coreless crucible induction furnace consists of a water-cooled helical coil surrounding a ramming mixture of monolithic refractory lining, forming a crucible in which a metallic mass to be melted is charged. Typically, the Coreless induction furnace works on a similar principle as that of a transformer. The primary module is formed by helically wound, very pure low resistivity electrolytic copper tubes through which cooling water flows. It is a pre-conditionthat water must be specially treated to prevent scale forming in the path. Generally, to get efficient results the coil is divided into several parallel circuits. Each turn is kept properly insulated with proper spacing during monolithic refractory lining / during running of the furnace.

[0006] Further, the coil is surrounded by a number of lamination packets constructed of laminated transformer iron steel. The crucible assembly consists of coil lamination packets, attop and bottom sections. The top and the bottom ring are bolted together to form a " squirrel case" Furthermore, the coil is clamped vertically by a top and bottom fabricated unit to prevent vertical channel, pads and jacking bolts. The complete coil assembly is fitted in a fabricated steel structure which is hydraulically tilted.

[0007] During operation when power is fed to the furnace coil through flexible water-cooled cables, which with rubber hoses carry cooling water to and from the coil to compensate IA2 Rt losses resulting through the coil as well as conduction losses of heat through lining to helical coil assembly. Also, a limit switch is provided to switch off the power to hydraulic power pack when furnace tilts >95°C.

[0008] In operation, due to melting, following forces are regularly generated in monolithic lining / coil cradle assembly / crucible structure. A mechanical force i.e., high compressive strength on bottom refractory crucible proportional to density and height of metal being melted. Another mechanical force i.e., wear due to electromagnetic stirring resulting from eddy effect and skin depth proportional to frequency of furnace, power rating, crucible size, degree of superheat above melting point, metal fluidity etc. Yet another mechanical force i.e., abrasion due to electromagnetic force resulting from eddy effect and skin depth proportional to frequency of furnace, power rating, crucible size, degree of overheating above melting point, metal fluidity etc. Yet another mechanical force i.e., vibration due to electromagnetic force resulting from eddy current effect and skin depthproportional to design of equipment, frequency of furnace, power rating, crucible size, degree of under charging / overcharging, intermittent spacing between oversize / heavy charge etc. Yet another mechanical force i.e., fumes and vapour penetrates to the side wall of refractory due to electromagnetic eddy current effect and skin depth proportional to design of equipment, frequency of furnace, power rating, crucible size, degree of under charging / oversized charging, thermal conductivity of charge, intermittent spacing between oversize / heavy charge, bridging of charge, overheating of liquid metal due to faulty operation, volatile low temperature melting / b oiling point charge, late addition of low boiling point metal addition, gas purging / fluxing / flushing. Yet another mechanical force i.e., chemical reaction between refractory and metal being melted resulting due to electromagnetic force resulting from eddy current effect and skin depth proportional to design of equipment, frequency of furnace, power rating, crucible size, degree of under charging / oversized charging bridging of charge, overheating of liquid metal due to faulty operation, volatile low temperature melting / boiling point charge, late addition oflow boiling point metal addition, gas purging / fluxing / flushing. Yet another mechanical force i.e., combination of above all during initial charging - poking of charge / pressing of charge, slag removal, spooning of slag tapping of liquid metal. Yet another mechanical force i.e., thermal stress of frequent cooling and heating. Yet another mechanical force i.e., spalling, cracking, chipping due to mechanical action for removal of sticky metal / slag / dross / burnt refractory / damaged refractory. Additionally, there could be electrical and mechanical damages due to short circuit power failure.

[0009] Also, frequent temperature drop of liquid metal is prevalent due to high conductivity of fresh Copper and copper base alloys. Further, there could also be refractory damage due to frequent cleaning of side wall sticky slag.

[0010] In view of the above considerations, the present invention seeks toovercome the above-mentioned problems existing in the prior art and provides for a refractory lining with improved properties.Objects of the Present disclosure

[0011] It is an object of the present invention to provide for a Refractory lining which helps to avoid Sintering Process while operating at a lower cost and being most economical.

[0012] It is another object of the invention to provide for a refractory lining with optimal heat capacity. The refractory lining promotes less usage of Castable coil coat and avoids Copper Former. Further, the invention promotes lesser time for Refractory Formation at a low cost together with reduced production cost per MT of liquid metal. Also, the lining introduces least Metal losses in first batch production after monolithic development of Bonding.

[0013] It is yet another object of the present invention to provide for a Refractory lining chemically compatible & Metallurgical compatible as well as suitable for Aluminium and different alloys of Aluminium, Copper and different alloys of Copper, Zinc and Zinc Alloy, Magnesium and Magnesium Alloys, Nickel and Nickel alloys, Lead and Lead Alloys, Tin and Tin Alloys, Titanium and Titanium alloys, Product I Regrading of Ferro Alloys, Iron and High Alloyed Iron ( Cr -30% or higher).

[0014] It is yet another object of the present invention to provide for a refractory with which exhibits excellent compatible behaviour against different failure due to Melt line erosion, i.e., metal / slag reactions, melt line Slag built-in, melt line wear out or metal stirring, Side lining and fast taper I Bottom erosion, Elephant Foot type Erosion / Failure and metal penetrations through Antenna.

[0015] It is yet another object of the present invention to provide a lining with high compressive strength and resistance against wear which protects Refractory Failure / damages due to impact of charging, removing Slag and oxides, alloyaddition and exothermic reaction, high erosion due to Oxidised condition (High 02 level), mechanical forces of 95ntilting, longer Holding / Sampling, holding due to breakdown and metal distribution, temperature rise due to sampling, late addition, exothermic contamination, sudden oxidation (metal boiling) and Faulty charging.

[0016] It is yet another object of the present invention to provide Refractory lining compatible with monolithic lining which shows flexible lining replacement for different metal / grades, partial replacement of lining or sintered zone, better Insulation to avoid heat content, better heat absorption and heat content, promoting a varied combination of thermal expansion v / s contraction among different zone. Further, it promotes an economical and reliable installation with a power saving of 3 to 7%. It has production & sustainable productivity with lesser generation of slag &disposal coupled with higher recovery of charge, late addition & ferro alloys which can withstand exothermic reaction I explosion / boiling of metal.

[0017] It is yet another object of the present invention to promote less consumption of Refractory / MT of Production, which permits degassing, addition of deoxidant, N2, Ar gas at different metal level. It permits intermittent operations with continuous production that is suitable for STD Sintering @ with Flame, Extra bonding agent ( Na4B2O7.xH2O or Na2SiO3 or Boron Oxide or other proprietary material) and adaptable for Cast Iron pot / Precast Alumina Pot, Graphite / Silicon Carbide / ZrO2 or Brick Lined Acidic Si02, Magnesia, Sillimanite, Alumina, or Special Bricks.

[0018] It is yet another object of the present invention to develop other alternative way of A12O3 based neutral monolithic refractory lining for Nickle and Nickle base alloy including Stainless-steel metals and alloys therein.

[0019] It is yet another object of the present invention to facilitate the reusability of the MS former and

[0020] Furthermore, an additional objective of the present invention is to advance monolithic refractory development utilizing oxy-fuel heating.

[0021] SUMMARY

[0022] In a first aspect, the present invention provides a method for configuring a monolithic refractory lining, beginning with the pre-operative assessment of the induction furnace. This includes verifying coil functionality via hydrostatic and pneumatic testing, ensuring electrical insulation through varnish application, applying a high-alumina based cement (5 mm to 25 mm thick) for coil protection, and curing the castable cement to ensure the structural and electrical readiness of the crucible.

[0023] In a second aspect, the invention involves fulfilling pre-operative refractory requirements. This step comprises applying an air-dried varnish, properly earthing the crucible structure, installing an initial 10 mm to 25 mm uniform layer of coil coat utilizing high-alumina cement mortar, filling gaps between the live and dummy coils, and allowing for natural and strengthdevelopment curing cycles to prepare the crucible for the refractory lining process.

[0024] In a third aspect, the present invention details the formulation of the refractory lining comprising specific raw materials. The composition includes: 90% alumina dense castable (particle size 0 to 4 mm) comprising a minimum of 85% Al203, a maximum of 6% CaO, a maximum of 1% Fe2O3, and 10-15% water; an acidic silica ramming mass comprising a minimum of 99.5% Si02and a maximum of 0.30% FeO; a neutral alumina ramming mass and a sodium silicate (Na2SiO3) binding agent.

[0025] In a fourth aspect, the invention provides a method for the pre-operative preparation of the refractory mixture. The method comprises mixing a selected silica ramming mass with 1.2% to 2.0% LR grade boric acid, adding 2% to 6%sodium silicate binder to form uniform spherical balls, and exposing the mixture to dry C02gas to develop a scratch hardness exceeding 90. This standardized hardening process prepares the full batch for monolithic crucible lining.

[0026] In a fifth aspect, the invention provides a method for the final assembly of the refractory lining. The method comprises: placing insulation layers at the crucible bottom; ramming the bottom 50-65% height with a binder-free silica ramming mass, and the remaining 35-50% height with the binder-mixed silica ramming mass; utilizing a reusable mild steel (MS) former to prepare side linings layer-by-layer; passing dry C02gas through equidistant holes in the MS former to cure the mass; pre-heating the MS former with an oxyfuel burner to 900-1250 °C, followed by rapid cooling (via blowers or N2gas) to facilitate the easy extraction of the former, yielding a fully developed, high-strength monolithic lining.

[0027] In further aspects, the resulting refractory lining yields significant metallurgical and operational advantages over conventional linings. The invention provides:• Elimination of Sintering: By utilizing C02gas curing and an MS former, the lengthy 6 to 15-hour sintering cycle traditionally required for copper and copper alloys is entirely eliminated, reducing metal oxidation and loss. • Reusable Tooling: The method employs a reusable MS former, replacing non-reusable copper formers found in the prior art.• Enhanced Durability: The lining operates safely at finishing temperatures of 1380 °C to 1450 °C, developing three distinct refractoriness zones that resist thermal stress, metal penetration, slag reactions, and elephant foot type bottom erosion.• Operational Flexibility: The system permits flexible batch -to -batch production of various copper grades, including high-purity copper using neutral alumina refractories without requiring specialized initial sinterheats, while drastically reducing the time required for lining removal and preparation.

[0028] BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.

[0030] FIG 1 A illustrates a schematic diagram of an induction furnace with ramming mass, according to the existing state of art.

[0031] FIG IB illustrates a schematic diagram of an induction furnace with ramming mass, according to the present invention.DETAILED DESCRIPTION

[0032] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the disclosure.

[0033] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.

[0034] If the specification states that a component or feature "may”, "can”, "could”, or "might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0035] As used in the description herein and throughout the description that follow, the meaning of "a,” "an,” and "the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in” includes "in” and "on” unless the context clearly dictates otherwise.

[0036] The use of "including”, "comprising” or "having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms "a” and "an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. Further, the use of terms "first”, "second”, and "third”, and the like, herein does not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

[0037] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This invention may, however, be embodied in many different forms and should notbe construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skilled in the art. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).

[0038] The present invention relates to a method and structure for configuring a refractory lining in an induction furnace and other metallurgical auxiliary equipment, particularly suited for copper and copper base alloy industries. The invention provides a monolithic refractory lining that overcomes the drawbacks of conventional methods by eliminating lengthy sintering cycles and preventing common failure modes such as metal / slag reactions, metal penetration, and "elephant foot" type erosion.

[0039] Referring to Fig 1A illustrates a vertical cross-section of a coreless induction furnace designed for standard copper melting in accordance with existing prior art. It details the structural arrangement of the refractory lining, the former, and the induction coil assembly. The central area represents the internal crucible (1) space where the standard copper melting process occurs. Immediately surrounding the melting cubicle (1) is a metallic boundary MS (Mild Steel) Reusable Former (2) of thickness to be between 6 mm to 12 mm. This former acts as a structural mold to hold the refractory mass in place while the crucible is being prepared. The region surrounding the sides of the former represents the functional refractory lining (3). It is composed of a Silica Ramming Mass containing a maximum of 2% to 6% binder. This mass is rammed between the coils and the former to create the high-strength monolithic walls. The base or bottom section (4) of the furnace lining is distinct from the side walls. It is composed of a Silica Ramming Mass without a binder that constitutes 40% to 60% of the bottom refractory composition. Between the refractory mass and the outer coil structure, there is a thin layer (5) indicated as 1 to 3 mm thick (labeled "WITHE HEAT - A"), which typically serves as an electrical, thermal, or protective barrier (like mica or an insulation sheet) between the induction coils and the ramming mass. The outermost vertical sections depict the structural shell and thestacked induction coils. These coils generate the electromagnetic field required to melt the charge.

[0040] Referring to Fig IB, illustrates a vertical cross-section of an induction furnace configured for standard copper melting, showcasing the structural arrangement of the refractory lining and the patented former assembly according to the present invention. The central area represents the internal crucible (102) space designed for standard copper melting. Immediately surrounding the melting cavity is a boundary labeled as an MS (Mild Steel) Reusable Former (104) of thickness to be 6 mm to 12 mm, wherein this structural mold is a key aspect of the invention, utilized to hold the refractory mass in place during preparation and is designed to be reusable. The upper bottom and side wall refractory lining (106) composed of Alumina / Silica Ramming Mass with Metal Silicate Binder (Mx.(SiO3)yxH2O). This highlights a distinct material composition compared to the conventional state of the art. The lowermost foundational base (108) of the furnace lining is composed of a Silica Ramming Mass without a binder. This illustrates the multi-zone-bottom construction methodology of the invention. Separating the functional refractory mass from the outer coil structure is a thin boundary layer (110) indicated as 1 to 3 mm thick (labeled "WITHE HEAT - A"). This layer serves as a necessary thermal, electrical, or physical protective barrier. On the far left and far right outer peripheries, a vertical stack of rectangular blocks is visible. These represent the cross-sections of the induction coils that wrap around the crucible to generate the electromagnetic melting field.

[0041] The following embodiments describe various aspects of the refractory lining, its composition, and its method of assembly.

[0042] In a first exemplary embodiment, the invention comprises a systematic pre-operative assessment and preparation of the induction furnace to ensureelectrical and structural integrity prior to lining. This embodiment is executed in two primary stages:Stage 1: Furnace Assessment include steps of:conducting hydrostatic pressure tests of the induction coil and pneumatic tests of the hydraulic tilting mechanisms;checking the coil cradle for loose connections and ensuring all parameters of the power panel are suitable for full-power operations;applying F-class varnish for electrical insulation;applying a high-alumina based cement (having a thickness of 5 mm to 25 mm, depending on the crucible size) for coil protection; anddrying the castable cement for 12 to 48 hours, followed by a secondary check of electrical parameters and insulation of the structure, busbar, and cap-rack.Stage 2: Crucible Preparation including steps of:applying a sufficient coat of air-dried varnish and ensuring proper earthing of the crucible structure;installing an initial layer of coil coat using high-alumina cement mortar; filling gaps between the live coil and the dummy coil, followed by installing a gentle, uniform layer of 10 mm to 25 mm thickness; andsubjecting the configuration to a curing cycle of 12 to 48 hours for proper strength development (or natural curing for 24 to 72 hours in high-humidity conditions) prior to the core refractory lining process.

[0043] In a second embodiment, the invention details the specific raw materials and the preparation process of the monolithic refractory mixture to achieve a desired scratch hardness without conventional sintering. The refractory mixture consists of 90% alumina dense castable is having a particle size of 0 to 4 mm. Thechemical composition comprises a minimum of 85% A12O3, a maximum of 6% CaO, a maximum of 1% Fe2O3, and 10% to 15% water; a silica-based ramming mass comprising a minimum of 99.5% Si02and a maximum of 0.30% FeO; and binder that includes Sodium silicate (Na2SiO3).

[0044] In accordance with one of the embodiments, the pre-operative mixing and hardening including steps of: mixing a selected silica ramming mass of a desired particle size distribution thoroughly with 1.2% to 2.0% LR grade boric acid. To establish quality assurance, a proportionate sample (1 kg to 10 kg) is drawn. To this sample, 2% to 6% sodium silicate binder is added to form uniform spherical balls. Dry C02gas is passed over the sample to develop a scratch hardness of greater than 90. Upon verification of the scratch hardness, the full batch of the monolithic refractory mixture is prepared using the exact proportions to achieve identical hardness parameters, rendering it ready for induction crucible lining.

[0045] In the third embodiment, the invention comprises the physical structural assembly of the refractory lining inside the crucible, utilizing a reusable former and a gas-curing mechanism. This enables the development of three distinct zones of refractoriness. The Bottom and Side Wall Assembly includes 2 to 3 layers of insulation paper that are placed at the bottom of the crucible; the bottom of 50-65% height is prepared with the silica ramming mass without a bonding agent. The remaining 35-50% height of the bottom is prepared with the binder-mixed silica ramming mass comprising a minimum of 99.5% Si02and a maximum of 0.30% FeO. A reusable Mild Steel (MS) former is placed inside, ensuring proper centering. The side lining is prepared layer-by-layer by poking and pressing the refractory mixture between the former and the crucible wall up to the top level. MS or Stainless Steel (SS) wire mesh is integrated into the silica ramming mass to prepare the non-functional furnace top and pouring spout.

[0046] In accordance with the third embodiment, the Curing and Extraction Process including steps of: applying a reusable MS former is configured with equidistant and equi-spaced holes having a diameter of 1.5 mm to 3 mm; passing dry C02gas through these holes to cure the surrounding monolithic refractory mass; pre-heating the reusable MS former using a long-flame oxyfuel burner to temperatures between 900 °C and 1250 °C; and allowing rapid cooling via mancoolers, blowers, or N2gas passing, which shrinks the MS former and facilitates its fast and easy removal. The crucible is then immediately ready for batch production.

[0047] In a fourth embodiment, the refractory lining is adapted specifically for high-purity copper and copper base alloy production. While conventional systems strictly rely on silica refractories for such applications, this embodiment utilizes an alumina-type neutral ramming mass. Because the conventional 6 to 15-hour sintering cycle is entirely eliminated, extreme metal oxide formation is prevented. Furthermore, this embodiment removes the requirement for "wash heats" or "sinter heats" (where the first heat must be limited to less-impurity copper grades). Instead, the neutral refractory allows for flexible, batch -to -batch production of variable, high-purity copper grades immediately upon commissioning of the furnace, significantly reducing metal loss and overall preparation downtime (from the conventional 8 to 36 hours down to a fraction of the time).

Claims

CLAIMS:I / We claim:

1. A method for assembling a monolithic refractory lining in an induction furnace, the method comprising:performing a pre-operative furnace assessment and preparing a crucible structure;preparing a monolithic refractory mixture comprising a ramming mass and a binder;placing 2 to 3 layers of insulation paper at a bottom of the crucible; preparing a first bottom zone comprising 50% to 65% of a total bottom height utilizing a silica ramming mass without a bonding agent; preparing a second bottom zone comprising a remaining 35% to 50% of the total bottom height utilizing the monolithic refractory mixture containing the binder;placing a reusable mild steel (MS) former centrally inside the crucible, wherein the MS former comprises a plurality of equidistant and equispaced holes;preparing a side lining layer-by-layer by packing the monolithic refractory mixture between the reusable MS former and a wall of the crucible;passing dry C02gas through the plurality of holes of the reusable MS former to cure the monolithic refractory mixture;pre-heating the reusable MS former using a long-flame oxyfuel burner to a temperature between 900 °C and 1250 °C; andrapidly cooling the reusable MS former to facilitate structural shrinkage and removal of the reusable MS former from the crucible without the need for a conventional sintering cycle.

2. The method as claimed in claim 1, wherein performing the pre-operative furnace assessment comprises:conducting hydrostatic pressure tests of an induction coil and pneumatic tests of hydraulic tilting mechanisms;applying F-class varnish for electrical insulation;applying a 5 mm to 25 mm thick layer of high-alumina based cement for coil protection; anddrying the castable cement for 12 to 48 hours.

3. The method as claimed in claim 1, wherein preparing the crucible structure comprises:applying an air-dried varnish and earthing the crucible structure; installing an initial layer of coil coat using high-alumina cement mortar; installing a uniform layer of 10 mm to 25 mm thickness; and subjecting the crucible structure to a curing cycle of 12 to 48 hours for strength development.

4. The method as claimed in claim 1, wherein the monolithic refractory mixture comprises:a. a 90% alumina dense castable having a particle size of 0 to 4 mm, further comprising a minimum of 85% Al203, a maximum of 6% CaO, a maximum of 1% Fe2O3, and 10% to 15% water;b. a silica-based ramming mass comprising a minimum of 99.5% Si02and a maximum of 0.30% FeO; andc. a sodium silicate (Na2SiO3) binder.

5. The method as claimed in claim 1, wherein preparing the monolithic refractory mixture further comprises:mixing a selected silica ramming mass thoroughly with 1.2% to 2.0% LR grade boric acid;extracting a proportionate sample of 1 kg to 10 kg and adding 2% to 6% of a sodium silicate binder to form uniform spherical balls;passing dry C02gas over the sample to develop a scratch hardness greater than 90; andpreparing a full batch of the monolithic refractory mixture utilizing identical proportions, upon verification of the scratch hardness to achieve identical hardness parameters.

6. The method as claimed in claim 1, wherein the plurality of equidistant and equi-spaced holes on the reusable MS former have a diameter ranging from 1.5 mm to 3 mm.

7. The method as claimed in claim 1, further comprising integrating a mild steel (MS) wire mesh or a stainless steel (SS) wire mesh into the monolithic refractory mixture to prepare a non-functional furnace top and a pouring spout.

8. The method as claimed in claim 1, wherein rapidly cooling the reusable MS former is achieved by applying forced air via man-coolers, blowers, or passing N2gas.A refractory lining composition for an induction furnace, such composition comprising:an alumina dense castable fraction having a minimum of 85% A12O3; a silica ramming mass fraction having a minimum of 99.5% Si02and a maximum of 0.30% FeO;1.2% to 2.0% LR grade boric acid; and2% to 6% sodium silicate binder.

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